Conventionally, there is known a feedback control (hereinafter referred to as F/B control) that brings a physical value influencing the combustion of the internal combustion engine closer to a suitable value (target value) corresponding to a driving state. There are objects to be F/B controlled, such as an opening degree of a throttle valve, a supercharging efficiency of a supercharger (turbocharger), an opening degree of an EGR valve of an exhaust gas recirculation (EGR) device, and a phase of opening and closing of each of an intake valve and an exhaust valve in a variable valve timing mechanism.
Recently, it is requested to concurrently perform plural F/B control processes in order to further reduce the fuel consumption and the emission of the internal combustion engine. It is known that control processes interfere with each other when the objects are F/B controlled concurrently. For example, a supercharging efficiency of the turbocharger is changed to bring the supercharging pressure closer to a target value, whereby an EGR amount is changed even when an opening degree of the EGR valve is constant. Also, an opening degree of the EGR valve is changed to bring the EGR amount closer to a target value, whereby a supercharging pressure is changed even when the supercharging efficiency of the turbocharger is constant. In this way, when the objects are F/B controlled in parallel, the F/B control influence each other. It is thus difficult for the F/B control to converge.
As a technique where the objects are F/B controlled in parallel, Patent Document 1 discloses a technique where control values of two control inputs are calculated by a response designating algorithm commonly using the same given linear function, and the F/B control of the internal combustion engine is performed based on the calculation result to improve stability of the F/B control.
Also, Patent Document 2 discloses a technique that may relate to the present invention.